Question

Extraction of copper is done using copper pyrites. After roasting, the ore is mixed with silica and coke and then smelted in a blast furnace. The matte obtained from the blast furnace is charged into a silica-lined converter. Some silica is also added, and a hot air blast is blown into the mixture to obtain blister copper, which is purified by electrorefining. The chemical composition of the slag formed during smelting is:

• A. ${\mathrm{CuSiO}}_3$
• B. ${\mathrm{CaSiO}}_3$
• C. ${\mathrm{FeSiO}}_3$
• D. None of these

Answer 1

The correct option is C

${\mathrm{FeSiO}}_3$

The explanation for Correct answer:

Option (C) ${\mathrm{FeSiO}}_3$

• The process of extracting metals from their ores is called metallurgy.
• The less reactive metals can be extracted by converting the ore into metallic oxide and by reducing it into free metal.
• The conversion of ore to metallic oxide can be done by calcination and roasting.
• Calcination is the process of heating to a high temperature below the melting point of metal in absence of air or a limited supply of air
• Generally, calcination is utilized to convert Hydrated oxides or Hydroxides and Carbonates into respective oxides.
• Roasting is the process of heating to a high temperature below the melting point of metal in presence of air or oxgen.
• Generally roasting is utilized to convert Sulphide ores to respective Oxides.
• Copper pyrites are the ore of Copper in which Copper is present in the form of its Sulphide.
• Here the reverberatory furnace is used, so this gives a roasting reaction to give Copper oxide as the main product.
• Copper pyrites also contain iron, so it is treated with some amount of silica in order to remove iron as slag.$\underset{\mathrm{Copper}\mathrm{sulfide}}{{\mathrm{Cu}}_2\mathrm{S}\left(\mathrm{s}\right)}+\underset{\mathrm{Iron}\mathrm{sulfide}}{\mathrm{FeS}\left(\mathrm{s}\right)}\stackrel{{\mathrm{O}}_2}{\to }\underset{\mathrm{Copper}\mathrm{oxide}}{{\mathrm{Cu}}_2\mathrm{O}\left(\mathrm{s}\right)}+\underset{\mathrm{Iron}\mathrm{oxide}}{\mathrm{FeO}\left(\mathrm{s}\right)}+\underset{\mathrm{Sulphur}\mathrm{dioxide}}{2{\mathrm{SO}}_2\left(\mathrm{g}\right)}$
• Ferrous oxide combines with sand to form a fusible slag.$\underset{\mathrm{Ferrous}\mathrm{oxide}}{\mathrm{FeO}\left(\mathrm{s}\right)}+\underset{\mathrm{Flux}}{{\mathrm{SiO}}_2\left(\mathrm{s}\right)}\to \underset{\mathrm{Slag}}{{\mathrm{FeSiO}}_3\left(\mathrm{s}\right)}$.
• Hence Option C is correct.

The explanation for incorrect answer:-

Option (A) ${\mathrm{CuSiO}}_3$

• During Copper extraction, the Cuprous oxide formed combines with Ferrous sulfide to give Ferrous oxide and Cuprous sulfide.

$\underset{\mathrm{Ferrous}\mathrm{sulfid}}{\mathrm{FeS}\left(\mathrm{s}\right)}+\underset{\mathrm{Cuprous}\mathrm{oxide}}{{\mathrm{Cu}}_2\mathrm{O}\left(\mathrm{s}\right)}\to \underset{\mathrm{Ferrous}\mathrm{oxide}}{\mathrm{FeO}\left(\mathrm{s}\right)}+\underset{\mathrm{Cuprous}\mathrm{sulfide}}{{\mathrm{Cu}}_2\mathrm{S}\left(\mathrm{s}\right)}$

• This is due to the greater affinity of Iron for Oxygen than Copper.
• Hence Option A is incorrect.

Option (B) ${\mathrm{CaSiO}}_3$

• Since iron has the greatest affinity for oxygen, Ferrous oxide reacts with sand to form a fusible slag.
• Hence option B is incorrect.

Option (C) None of these

• Here, Option (A) ${\mathrm{CuSiO}}_3$ is correct.
• So, it is not possible to be none of the above.

Therefore, option (C) ${\mathrm{FeSiO}}_3$ is the correct answer.